KR100290079B1 - Resin composition for automobile bumper cover excellent in impact resistance - Google Patents

Abstract

The present invention relates to a resin composition for an automobile bumper cover having excellent impact resistance and fluidity and improved paintability, and more specifically, to a crystalline polypropylene resin of a partial crosslinking system, a predetermined amount of crystalline polypropylene and an inorganic filler are blended. By adding the polypropylene resin of the master batch, the resin composition for automobile bumper cover, which has various fluidity and excellent paintability, and obtains rigidity and impact strength suitable for automobile bumper cover while reducing the content of expensive rubbers. It is about.

Description

Resin composition for automobile bumper cover excellent in impact resistance

The present invention relates to a resin composition for an automobile bumper cover having excellent impact resistance and fluidity, and having an improved coating, and more particularly, to a crystalline polypropylene resin of a partial crosslinking system, in which a predetermined amount of crystalline polypropylene and an inorganic filler are blended. By adding the polypropylene resin of the master batch, the resin composition for automobile bumper cover, which has various fluidity and excellent paintability, and obtains rigidity and impact strength suitable for automobile bumper cover while reducing the content of expensive rubbers. It is about.

Automobile bumper covers are largely classified into soft type and hard type, and the classification criteria are flexural modulus expressing the rigidity of the material. That is, those with a flexural modulus of 6000 kgf / cm ² are classified as soft, and those having 12,000 kgf / cm ² or more are classified as hard. In the case of the soft type, the flexural modulus is controlled by blending with crystalline polypropylene by using the low rigidity of rubbers, but rubbers should be blended at 30 to 40% in order to obtain rigidity that meets the standard. The use of expensive rubbers at high contents is disadvantageous in terms of cost, but there is still no technical progress to achieve softness while reducing the content of rubber.

Accordingly, the present inventors have focused on developing a material that can replace rubber, which is one component constituting the resin composition for automobile bumper cuppers, and has concentrated on researching the alternative of rubbers of amorphous polypropylene.

Amorphous polypropylene is called atactic polypropylene (APP) by the classification according to the crystal structure of polypropylene, has a low crystallinity is significantly lower than the isotactic crystallinity has flexibility, impact resistance and low shrinkage characteristics have. It is mainly formed as a by-product in the process of producing crystalline polypropylene, or is developed and produced using a metallocene catalyst which is recently spotlighted by Rexene of USA (US Pat. No. 5,723,546). The latter Rexene product itself is excellent in terms of completeness, but the rubber substitute material is not much in terms of price. In the former case, in order to increase the crystallinity after polymerization in the process of producing crystalline polypropylene, a certain low molecular weight amorphous formed during polymerization is dissolved in an aliphatic hydrocarbon solvent such as heptane and then centrifuged. Since the number average is as low as 1,000 to 3,000 and is separated in the form of a bale lump, it cannot be used alone and cannot be injected and extruded into a finished product by itself.

The inventors of the present invention, while examining the rubber substitutes of such low molecular weight amorphous polypropylene, when the master batch (APP M / B) by mixing a certain amount of crystalline polypropylene and an inorganic filler in the amorphous polypropylene, a soft material In addition, it was found that it plays an excellent role as a modifier for improving the low mold shrinkage, low coefficient of linear expansion, impact resistance and flowability of the hard material, depending on the amount of use, and first applied for the polypropylene resin composition having such a configuration. Patent Application No. 1998-42211}.

Then, the present inventors blended a rubber-added master composition amorphous polypropylene resin developed in place of some or all of the rubbers added for impact reinforcement to the resin composition for automobile bumper cover, thereby reducing the content of expensive rubbers. The present invention was completed by confirming that reasonable stiffness and impact strength can be obtained.

Accordingly, an object of the present invention is to provide excellent impact resistance and fluidity in the resin composition for automobile bumper cover, which is composed by mixing amorphous polypropylene resin in a master batch in place of some or all of rubbers added for impact reinforcement. It is to provide a resin composition for automobile bumper cover with improved paintability.

The above and other objects of the present invention will become apparent from the following detailed description of the invention.

In order to achieve the above object, the resin composition for automobile bumper cover according to the present invention, (a) 40 to 70 parts by weight of amorphous polypropylene; (b) 10 to 30 parts by weight of crystalline polypropylene; And (c) an amorphous polypropylene resin composed of 5 to 30 parts by weight of an inorganic filler, in place of some or all of the rubbers.

That is, the resin composition for automobile bumper covers which concerns on this invention is 1-70 weight part of following (A) components with respect to 100 weight part of (A + B + E + F + G) resin or a rubber component; (B) 10-70 weight part of components; 0.01 to 10 parts by weight of (C) component; 0.01 to 2.0 parts by weight of (D) component; (E) component 1-30 weight part, (F) component 30 weight part or less; And (G) component 1 to 20 parts by weight.

(A) A homopolymer of propylene or a binary copolymer of propylene and 10 mol% or less of α-olefins having 2 to 10 carbon atoms, having a melt index of 0.1 to 3 g / 10 minutes (230 ° C.) and a weight average molecular weight of 300,000 g / crystalline polypropylene that is at least mol;

(B) a homopolymer of propylene or a binary copolymer of propylene and an α-olefin having 2 to 10 carbon atoms of 11 to 25 mol%, a crystalline polypropylene having a melt index of 10 to 60 g / 10 minutes (230 ° C.);

(C) vinyl type crosslinking aid;

(D) two or more organic peroxides having different decomposition temperatures;

(E) amorphous polypropylenes of the following composition;

(a) 40 to 70 parts by weight of amorphous polypropylene;

(b) 10 to 37 parts by weight of crystalline polypropylene; And

(c) 5 to 30 parts by weight of the inorganic filler;

(F) thermoplastic elastomer rubbers; And

(G) Inorganic fillers.

Among the above components, the components (A) to (D) form the crystalline polypropylene resin of the partial crosslinking system (Korean Patent Application No. 1998-10099). In the case of the crystalline polypropylene of the partial crosslinking system, its crosslinked structure acts as an impact modifier like a rubber or an elastomer, so it has excellent impact resistance, heat resistance and rigidity, as well as high melt index in a low melt index extruded product. It has a variety of fluidity to mold injection products.

Partial crosslinking system controls the crosslinking degree of the crystalline polypropylene itself, and the crosslinked structure acts as an impact modifier like a rubber or an elastomer through morphological control such that a small amount of the crosslinked structure becomes a dispersed phase and a resin having a high flow index becomes a continuous phase. I did it. This partial crosslinking system is a higher molecular weight in the crystalline polypropylene is more likely to be crosslinked than decomposition, and the degree of decomposition of the crystalline polypropylene can be controlled according to the decomposition temperature (half-life temperature) of the organic peroxide, the reaction initiator. . That is, in the presence of two kinds of organic peroxides and vinyl-based crosslinking aids having different decomposition temperatures, a crystalline polypropylene having a high weight average molecular weight and a crystalline polypropylene having a high content of α-olefin monomer and excellent fluidity are blended in an appropriate amount. The degree of crosslinking and flow can be controlled.

Since the crystalline polypropylene of such partial crosslinking system has excellent impact strength and rigidity in itself, it is possible to reduce the content of rubber added for the purpose of impact reinforcement. Further reducing the content of the rubber to obtain a stiffness and impact strength suitable for the car bumper cover even if replacing all of the rubber, it is possible to provide a resin composition for a car bumper cover having a low linear expansion and low shrinkage characteristics. In addition, the low molecular weight amorphous polypropylene is properly transferred to the surface during injection, exhibiting excellent penetration into the paint layer during coating, thereby improving the paintability.

Hereinafter, each component which comprises this invention is demonstrated.

(A) High molecular weight crystalline polypropylene:

As a component in which the crosslinking reaction occurs mainly, a homopolymer of propylene or a binary copolymer of propylene and an α-olefin having 2 to 10 carbon atoms, the content of α-olefin in the binary copolymer is 10 mol% or less, and the melt index is 0.1 to 3 g / 10 min (230 ° C.) and weight average molecular weight is preferably 300,000 g / mol or more, preferably 500,000 g / mol.

Although the kind of C2-C10 alpha-olefin polymerized with propylene is not specifically limited, For example, ethylene, butene-1, 4-methyl-pentene-1, hexene-1, octene etc. can be mentioned.

On the other hand, component (A) is a high molecular weight crystalline polypropylene added for partial crosslinking to express high impact. If the content is 1 part by weight or less, the crosslinking may not be sufficiently performed to express high impact, and 70 parts by weight. In the above case, excessive crosslinking results in low fluidity, making it impossible to produce a pellet in the extruder. Therefore, it is preferable to use (A) component at 1-70 weight part.

(B) Highly crystalline polypropylene:

Very good fluidity and high content of α-olefins with 2 to 10 carbon atoms, which can cause some crosslinking reaction in the α-olefin region. The homopolymer of propylene or α-olefin having 2 to 10 carbon atoms As the binary copolymer, the content of α-olefin in the binary copolymer is 11 to 25 mol%, preferably 15 to 25 mol%, and the melt index is 10 to 60 g / 10 minutes (230 ° C.), preferably 20 to It is good to use 60g / 10min (230 degreeC).

Component (B) is a crystalline polypropylene used to induce excellent fluidity when produced in pellet form in an extruder, more preferably when molded into a bumper by a molding company, and the content is less than 10 parts by weight. It is not effective for improvement, and if it is 70 parts by weight or more, the fluidity is excessive, and it is rather disadvantageous during molding, and the use of high molecular weight crystalline polypropylene of component (A) is relatively decreased, so that the crosslinking is not sufficient, which is good for high impact. not. Therefore, it is preferable to use (B) component at 10-70 weight part.

(C) vinyl-based crosslinking aid:

It is a component that suppresses decomposition of crystalline polypropylene during crosslinking and promotes crosslinking reaction and also improves paintability. Specifically, styrene, α-methylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, glycidyl (Meth) acrylate, butyl acrylate, vinyl acetate, vinyl benzoate, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, and the like, and preferably acrylate or methacrylate derivatives. It is preferable to use a mixture of styrene or its derivatives.

Component (C), when partially crosslinking the high molecular weight crystalline polypropylene of component (A) with an organic peroxide of component (D), serves as a bridge between the two components to aid crosslinking and to decompose the polypropylene. As a suppressing crosslinking agent, the content is less than 0.01 part by weight based on 100 parts by weight of the composition consisting of the component (A), (B), (E), (F) and (G). , The effect is insignificant, and the efficiency of (D) component is reduced and crosslinking of a preferable degree does not occur, and when it is 10 weight part or more, crosslinking becomes severe and fluidity falls like an excessive addition of (A) component, and it pellets in an extruder It is impossible to manufacture into a phase and has a bad smell and is not suitable for workers to work with. Therefore, it is preferable to use the vinyl crosslinking adjuvant of (C) component at 0.01-10 weight part with respect to 100 weight part of said compositions.

(D) Organic Peroxides:

As the component used as the reaction initiator, specifically, benzoyl peroxide, lauryl peroxide, dicumyl peroxide, bis (t-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (t-butyl) Peroxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexene-3, and the like, and two kinds having different decomposition temperatures may be used in combination to control fluidity. Lower decomposition temperature results in lower crosslinking efficiency but lower degree of decomposition of crystalline polypropylene; High ones show severe degradation.

When the organic peroxide of component (D) is used in an amount of 0.01 parts by weight or less based on 100 parts by weight of the composition consisting of component (A), component (B), component (E), component (F) and component (G), If the component cannot be crosslinked, and if it is used at 2.0 parts by weight or more, the component (A) is excessively crosslinked and fluidity is lowered, so that it cannot be produced in pellet form for bumper molding. Therefore, the organic peroxide of (D) component is used in 0.01-2.0 weight part with respect to 100 weight part of compositions which consist of (A) component, (B) component, (E) component, (F) component, and (G) component. It is desirable to.

(E) amorphous polypropylene resin:

A component that is blended in place of some or all rubbers for the purpose of impact resistance reinforcement and low shrinkage improvement constitutes a feature of the constitution of the present invention. In the present invention (a) 40 to 70 parts by weight of amorphous polypropylene; (b) 10 to 30 parts by weight of crystalline polypropylene; And (c) an amorphous polypropylene resin composed of 5 to 30 parts by weight of an inorganic filler.

Specifically, (a) amorphous polypropylene, a propylene homopolymer or a binary copolymer of propylene and ethylene of 10 mol% or less, having a mass average molecular weight of 20,000 to 200,000 g / mol, preferably 2 to 6 mol% of ethylene And the mass average molecular weight is 20,000 to 100,000 g / mol. Also, (b) a crystalline polypropylene, a propylene homopolymer or a binary copolymer of propylene and 20 mol% or less of α-olefins having 2 to 10 carbon atoms, having a mass average molecular weight of 300,000 g / mol or more, preferably ethylene content As the propylene-ethylene copolymer in the range of 4 to 10 mol%, a mass average molecular weight of 400,000 to 600,000 g / mol is preferably used. (C) As the inorganic filler, talc, calcium carbonate, calcium sulfate, magnesium oxide, calcium stearate, mica, silica, calcium silicate, clay, carbon black, and the like can be used. It is preferable to use it, and in order to supplement a physical property, it is preferable to use the talc of 2-20 micrometers of average particle diameters, Preferably it is 3-7 micrometers.

If the content of the component (E) is less than 1 part by weight, it does not contribute to the impact resistance reinforcement and the low shrinkage improvement. If the content is 30 parts by weight or more, the fluidity becomes high, making it impossible to produce a pellet. Therefore, it is preferable to use amorphous polypropylene resin of (E) component in 1-30 weight part.

(F) Thermoplastic elastomer rubbers:

As the component used for impact resistance reinforcement, ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), ethylene-octene copolymer (EOR), styrene-butadiene (SBR) and the like can be used. Among these, in the case of the ethylene-octene copolymer (EOR), the effect of improving the impact strength is remarkable due to the octene group of the long side chain, and the stiffness which is relatively lowered can be reduced as much as possible. The ethylene-octene copolymer has an octene content of 10 to 39%, preferably 23 to 25%, a melt index of 0.5 to 8 g / 10 minutes (190 ° C, 2.6 kgf), and a density of 0.868 to 0.885 g / cc. We use thing (ENGENG series of DuPont Dow Elastomer).

Component (F) is a conventional rubber component used for impact resistance reinforcement of the bumper resin composition. If the content is 30 parts by weight or more, the flexural modulus is sharply lowered, and thus it is impossible to use it as a bumper resin.

(G) Inorganic fillers:

As the component used for the rigid reinforcement, specifically, the same kind as those of the inorganic filler constituting the component (E) can be used. Among them, it is preferable to use talc having a marked increase in rigidity of the resin composition with increasing content, and a talc having an average particle diameter of 1 to 30 µm, preferably 5 to 10 µm.

If the component (G) is used in less than 1 part by weight, it does not contribute to the improvement of stiffness. If the content is 20 parts by weight or more, the rigidity is excessively increased and the impact resistance becomes weak, so it is impossible to use it as a bumper resin. Therefore, it is preferable to use (G) component at 0-20 weight part.

Hereinafter, the present invention will be described in more detail with reference to various examples.

The physical property evaluation method of the various compositions employ | adopted in the following Example and the comparative example was performed by the following test method.

(1) Melt index was measured by ASTM D-1238:

Test condition: 230 ℃, 2.16kgf

(2) Flexural modulus was measured by ASTM D-790 method:

Specimen size: 12.7 × 127 × 6.4mm

Crosshead speed 28 mm / min under test conditions

(3) Izod impact strength was measured by ASIM D-256 method:

Specimen size 63.7 × 12.7 × 3 mm

(4) Heat deflection temperature was measured by ASTM D-648 method:

Specimen size: 12.7 × 127 × 6.4mm

Load value used for test conditions: 4.6kgf

(5) Peel strength (180 °, Peel Strength) for paintability test is to apply two-component urethane-based paint to 50㎛ thickness without pretreatment, dry at 90 ℃ for 30 minutes, then leave at room temperature for 48 hours A test specimen for measurement was obtained. The test piece thus prepared was cut into a width of 1 cm and a length of 15 cm, and then measured by an Instron universal tester.

(6) Mold shrinkage is drawn on the injection mold with a standard length (140.3mm) mark, and the specimen is left for 24 hours at 23 ° C and 50% relative humidity, and then the length of the mark on the injection specimen is measured. Calculated using Equation 1:

[Equation 1]

Example 1-6

First, the components (A), (B) and (C) specified in Table 1 are mixed, and then (D), (E), (F) and (G) components are added thereto, followed by mixing for 3 minutes by a Henschel mixer. It was. The mixture was extruded at a temperature in the range of 190 to 250 ° C. with an extruder, and then cooled and solidified to obtain a pellet-like composition. The obtained composition was injected at a temperature range of 180 to 250 ° C. according to the melt index, and then various physical properties were measured according to the aforementioned methods. The results are shown in Table 1.

Example 7

In Example 1, except that the (F) component was not added, but instead of increasing the content of the (A) component, it was carried out in the same manner by combining the same components and contents as in Example 1, the above-described methods According to the various physical properties were measured. The results are shown in Table 1.

Comparative Example 1-2

Except not adding the component (E) in the Example, the same ingredients as in the Example was carried out in the same manner by mixing in the amounts specified in Table 1, and the various physical properties were measured in accordance with the above-described methods . The results are shown in Table 1.

In the resin composition for automobile bumper cover according to the present invention, by adding a predetermined amount of crystalline polypropylene and an inorganic filler to the crystalline polypropylene resin of the partial crosslinking system, an amorphous polypropylene resin obtained by master batching is added, thereby providing excellent fluidity and excellent flexibility. It has paintability, and can reduce the content of expensive rubbers and obtain stiffness and impact strength suitable for the bumper cover of an automobile.

Claims (4)

WHEREIN: The resin composition for automobile bumper covers WHEREIN: About (A) component 1-with respect to 100 weight part of resin compositions which consist of following (A) component, (B) component, (E) component, (F) component, and (G) component. 70 parts by weight; (B) 10-70 weight part of components; (E) component 1-30 weight part; (F) Component 0-30 weight part and (G) component 1-20 weight part, and 0.01-10 weight part of (C) component with respect to 100 weight part of said compositions; And (D) 0.01 to 2.0 parts by weight of a component, wherein the resin composition for a bumper cover for automobiles is: (A) a homopolymer of propylene or a binary copolymer of propylene and 10 mol% or less of an α-olefin having 2 to 10 carbon atoms Crystalline polypropylene having a melt index of 0.1-3 g / 10 min (230 ° C.) and a weight average molecular weight of at least 300,000 g / mol; (B) a homopolymer of propylene or a binary copolymer of propylene and an α-olefin having 2 to 10 carbon atoms of 11 to 25 mol%, a crystalline polypropylene having a melt index of 10 to 60 g / 10 minutes (230 ° C.); (C) vinyl type crosslinking aid; (D) two or more organic peroxides having different decomposition temperatures; (E) amorphous polypropylenes having the following composition; (a) 40 to 70 parts by weight of amorphous polypropylene; (b) 10 to 30 parts by weight of crystalline polypropylene; And (c) 5 to 30 parts by weight of an inorganic filler; (F) thermoplastic elastomer rubbers; And (G) inorganic fillers. The composition according to claim 1, wherein the component (a) is a propylene homopolymer or a binary copolymer having propylene and ethylene of 10 mol% or less, and having a mass average molecular weight of 20,000 to 200,000 g / mol. The component (b) according to claim 1, wherein the component (b) is a propylene homopolymer or a binary copolymer having propylene and 20 mol% or less of α-olefin having 2 to 10 carbon atoms, and having a mass average molecular weight of 300,000 g / mol or more. A composition characterized in that. The method according to claim 1, wherein each of the components (c) and (G) is selected from the group consisting of talc, calcium carbonate, calcium sulfate, magnesium oxide, calcium stearate, mica, silica, calcium silicate, clay, and carbon black. Compositions characterized in that the inorganic filler is at least one species.